Low-frequency magnetostrictive transducer



LOW-FREQUENCY MAGNETOSTRICTIVE TRANSDUCER Filed Jan. so, 1956 W. T. HARRIS 2 Sheets-Sheet l July 8, 1958 INVENTOR Muay/' [Ahmed BY i I ATTORNEYS 2,842,689 LOW-FREQUENCY MAGNETOSTRICTIVE TRANSDUCER Filed Jan. 30. 1956 W. T. HARRIS July 8, 1958 2 Sheets-Sheet 2 w %AW w INVENTOR ;xt 4502 fHAPP/J BY i ATTORNEYS LOW-FREQUENCY MAGNETOSTRECTHVE TRANSDUCER r .14 ciaims. (crew-ze .Myinvention relates to electromechanical transducers of the'type having application to acoustic transmission :and reeeption and to vibratory tools; it is also applicable V 'to transducer elements, as for underwater acoustic application and for employment in plurality in array configurations. This invention incorporates,improvenents and modifications with respect ?to copending applications Serial No. 475,462, filed December 15, 1954, Serial No. 558,947, filed January 1'3, :1956, and Serial No. 559,(557, filed January 17, 1956. r e

i It is an object of the invention to provide an improved transducer of the character indicated;

It is anothertobject to provide .a ,transdcer construc- "tion kof 'improved inherent etliciency and app'licable particularly to relatively low-frequency operation.

It is a further Object to providea magnetostrictive transducer Construction meeting the above objects ,and

enabling substantial economies in the use of"magnetostrictive material.

It is a still further objecttoprovde transducer con- 'struction meeting the above `'objectsancl inherentiy adaptable to relatively inexpensive assembly technique&

It is .also an object to provide a transducer meeting the above objects and featuring plural closedmagnetic flux- 'conducting paths, and yet pernitt-ing the developmentof electrical windings by means of conventional coil Windng techniques. V v i Other objects and various further ?features of novelty and invention will be pointed out or will occnxto those -skilled in the art from a reading of the following specification in conjunction with the accompanying drawings.

* In said drawings, Whichshow, for illustrative purposes only, preferred forms of the invention:

immersed' in a liquidmedium;

Fig. 3 'is a 'perspective view of a modified core according to the invention; i e

Fig. 4 is a similar view illnstrating the development of a windirg'linkedto the core of '-F ig.;3; i

fFigs. 5 and 6 :are end 'views of arrays of transducer elements of the general variety illustrated in Fig. 4, the difference between Figs. 5 and 6 being 'solely in the 'de- "tails of winding connections;

. 2 cations, whereby for any two adjacent ;legs a plurality `of longitudnally adjacent independent flux-;condncting `paths maybetdefined. The fluX-conducting means in 'termediate any two longitudinally adjacent flux-conductingpaths preferably acco-mmodates flux fromboth-paths in the same sense, and therefore adjacent paths are preferably -oppositely polarized. Since the adjacent paths are oppositely polarized, the separate Windings linked to the various paths must be developed inopp'osed senses, so that opposed ux circulation 'is developed in adjacent paths. In certain forms of the invention, the core is dedeveloped from a consolidated stack ofrlilre laminatiors in which the plural spaced llegs are integrally joined at head and tail ends, With permanent magnet inserts longitndinally intermediate said ends. In another form, the

separate legs are separately assembled as independent 'magneto-strictive core ll@ comprising a consolidated-stack of like laminations 11. Each lanination comprises a plu- 'rality of legs 12-13-14, which are similarly elongated and which are laterally spaced. First flux-.conducting means .15 joins first correspending ends ;of thelegs ili-14, and second vfluX-.conducting means 16 joinsthe other corresponding endsf of the Slegs 12-13-14'. In t .f ShOWI 'the 'first and second finX-conducting means 15-16 are tormed as integralpartsof thelarninations 11, and, for eonveniencgmay be termed head and tail portions. Third fluxconducting means is employed to connect corresponding intermediate portions ef adjacent *pairs of legs and, in the form shown, a first flnxconducting insert 1'7 is b onded to the adjacent legs 12-13, and a second finx-condcting insert Isis 'bondejd 'to the adjacent legs 13-14; an ,epoxy resin provides a satis' factory bonding agent. v V j j The described co-nstrnct-ion will be seen to establish plnral 'independent fiux-corducting paths, schematically indicated ;by the light phantom designations 19-52@- 21- 2'2f "FhlX of adjacentpaths .utilizes common flexcondncting means. ThuS, for example, the uX-onducting insert 17 ,serves fiux from both longitudinalty adjacent paths 19 and 29, and thelefthalfof the centerrleg -13 serves finxin -the adjacent paths 19-21; the width of center leg 13 is thus preferably substantially twicetle individual width of either of the outer legs 12-14, 'the outer-leg widths being preferably equal to each other. e

In order to mininize losses, I -prefer that fluX in adjacent paths shallbe gppositely polarized so that all tlnx 'travell-ing-in anyleg `ori 1ser t common .to ,two adjacent :path may t rvelin the same direction. Polarizing Wind ings may be employed for this purpose, but 'I prefer that -the inserts 17 shall be permanently magnetizedas, for example, of a suitablepermanently magnetizedterrite.

I have 'indicatd by meansof 'N-S legends 'on the face Fig. 7 is a simplified view in 'perspectve illnstratinga magnetostrictive element having a 'corerepresenting etur ther modification .of-the constructions of Figs. l and and i Fi'g. 8 'is .a horizontal sectional view the planes-3 'Brefly stated, my. invention contemplates longted Signal Wirding rn'ean s preferably inclides tnrns, inde pendently linled to alllegs 32-13-14 of thefcore 1 9. The direction oftnrns for-the' respective wind ings should be such as to establishfflux circilation in 'opposed 'sense in anytwo adjacent pathsi-'ZG-Zl-ZZ `This may be achieved by indepehdently developed wndings oneach of -the` various leg sections or by 'means of the basketweave type `'of'winding described ingreater detailin my `said ..co-,pending applicationserial No( 475,-462' an`d also shematically :llu'strated ;andtlater ;to b'eldescribed in connetonwithglig. .4. %Whateyerthemethodmf windy atnt ed July 8, -1 9 58 V u] ing development, the signal windings will have the appearance shown at 23-24 in Fg. 2, when assembled.

In order to economize on the use of magnetostrictive material, that is, in order to limit use of magnetostrictive material essentially only to fluX-circulating parts of the device, I illustrate in Fig. 2 the employment of counterweight members 25-26 which may be termed head and tail weights respectively, and bonded to the respective longitudinal ends of the stack 10. The counterweights 25-26 need not be laminated and are preferably of non-magnetic material. For example, they may be of aluminum, non-magnetic stainless steel, Zinc alloy, or of other desired alloy composition. The counterweights 25-25 are shown in Fig. 2 to provide a convenient means for mounting the transducer unit, as, for example, by bolting end fianges 27-28 o-f a mounting bracket thereto; it will be noted that the transverse offset bracl-:et portions adjacent flanges 27-28 may be sutciently yieldable so as not to impair longitudinal oscillation of the complete transducer. Finally, for those applications in which radiation is not required at both ends of the device, I illustrate acoustic pressure-release material 3:3 (e. g., cork, Wood, air-filled rubber, or the like) bonded to one longitudinal end, say the tail end 26 of the assembly.

In Fig. 3, l illustrate modification of the type of core construction illustrated in Fig. 1, the modification being in a manner permitting a more elorgated magnetostrictive body, as for application to lower frequencies. The core 31 of Figs. 3 and 4 may nevertheless closely resemble that of Fig. l. Thus, the basic lamination 32 from which the stack 31 is developed may again comprise spaced elongated legs 33-34-35 with fiuX-conducting means 36-37 joining the corresponding ends. In Figs. 3 and 4, however, I provide even greater pluralities of longitudinally adjacent flux paths, as developed by bonding (at plural longitudinally spaced locations) separate flux-conducting inserts 38-39-43 for the slot between adjacent legs 33-34, and 31-42-43 for the slot between adjacent legs 34-35. All inserts 38-39 43 are preferably permanent-magnet ferrite blocks, and bonding is preferably accomplished by means of a solvent-free agent, such as an epoxy resin. No legends have been applied to the various independent fluX paths developed by the described Construction, but the directional arrows indicate the opposed polarization of adjacent paths, and the winding means is preferably developed to circulate flux in adjacent paths in opposite directions.

As indicated generally above, the winding means may involve independent sets of turns linked to the respective legs of the various flux paths. However, in Fig.4, the winding, which is shown in simplified schematic form, may be developed from a single conductor extending between leads 45-46 and may employ the basket-weave development described in greater detail in my said copending application Serial No. 475,462. Thus, beginning at the lead 45, the winding may first enter over the top of leg 33 and run down the slot between legs 33 and 34, across the bottom of leg 34, up the slot between legs 34-35, across the top (at 47) and around and beneath the leg 35, across (at 48) the top of leg 34, down the slot between legs 33-34, across the bottom of leg 33, and around and over (at 49) the top of leg 33, and so on. Similar basket-weave developments may be followed for the linkage to legs 33-34-35 in the space longitudinally between inserts 38-39 and inserts 41-42, and so on; however, since adjacent fluX paths must be excited in opposite sense, the direction of basket-weave development longitudnally between inserts 38-39 and 41-42is ,opposite to that described at 47-48-49. Connection between these two successive basket-weave developments is illustrated at 50, where the conductor wraps around and therefore hides the insert 41. A similar connection 51 connects the basket-weave development between inserts 38-39 and 41-42, to the basketweave development between inserts 39-49 and 42-43, these two adjacent basket-weave developments being in opposed-phase relation. Finally, a connection 52 couples the last two basket-weave developments (again in opposed-phase relation), and the entire winding ends with the lead 46.

For all the forms thus far described, the polarization of flux patls and the excitation coupling thereto is such as to romote iri-phase magnetostrictive elongations for all parts of all legs so that the transducer may elongate and longitudinally resonate as a whole. Because the flux paths are short, there is negligible leakage along closely adjacent stretches of any one path, and highly efficient electromechanical energy Conversion is achieved.

in Figs. S and 6, I illustrate application of my magnetostrictve transducer Construction to arrays employing a plurality or like core elements 55 in side-by-side relation. The views of Figs. 5 and 6 are end views so that only one such element 55 is Visible. Nevertheless, it will be understood that the head and tail ends of all elements 55 of the array may be bonded to common head and tail members 56-57, and the latter may include a threaded or otherwise formed adapter means 53 for attachment to a mounting bracket (not shown). For protection, relatively flexible side panels 59-66* may be Secured to the head and tail members 56-57; the enclosed space may be liquid-fllled, or may be free-flooded with the liquid medium in which the transducer is to be operated.

In the arrangement of Fig. 5, a single lead-in supply 60 serves all windngs between longitudinally adjacent ux paths, so that the conductors 61-62 are shown connected :at the ends of the end windings 63-64. On the other hand, in Fig. 6, the lead-in supply 69' includes conductors 61'-62' serving all but one of the windings, namely, from the end winding 63' to the winding 64' next to the last winding 65. The last winding 65 is shown with independent lead connections 66 which may be used for feed-back purposes in a self-excited transducer, employed as described ,in greater detail in my copending .application Serial No. 524,545, filed July 26, 1955.

In Figs. 7 and 8, I illnstrate application of the principles of my invention to a magnetostrictive transducer element in which coil windings may be developed on coreleg sections .prior to assembly of the core legs to each other. Thus, the core legs 76-71-72 may ccmprise independent stacks of uniform strips of magnetostrictive material, the width of the strips of leg 71 being substantially twice the individual widths of outer legs 70-72, because, of course, the central leg 71 serves laterally adjacent fluX paths. First uX-conducting means 73-74 connects first correspondng ende of the legs 70-71-72; second flux-conducting means 75-76, at longitudinally spaced but corresponding locations, connects adjacent legs 70-71 and 71-72; and third ux-conducting means 77-78 connects the legs 70-71-72 at a third longitudinal location.

Since the connecting means 73-74 73 are not relied upon for longitudinal magnetostrictive elongation, they may be independent elements of magnetic flux-conductng material not having particular magnetostrictive properties. Accordngly, the end elements 73-74 and 77-78 may be of ferrite ceramic, and the intermediate inserts or blocks 75-76 between longitudinally adjacent flux paths are preferably ferrite permanent magnets.

Blocks 75-76 should 'be of thickness (determining lateral spacing of stacks 70-71 and 71-72) sufiicient to supply the required magnetomotive force and of width (longitudinally along the legs 70-71-72) suicient to pass the required magnetic flux. The ferrite blocks 73-74-77- 78 should be magnetically soft and have high permeability, high saturation flux density, and low coercive force. i

aaaaaea The mechanical assenbly of Figs. 7 and 8 is completed by applying a-solid head Weight 79 to one longitudinal endand ;a solid tail weight to the other longitudinal end. -Eachof the weights 'is 80 may be precision cast with arecess or cavity (or plural recesses or cavities) -formed to closely receive the projecting ends of the legs 70-71-72, and the assembly is'retained by bonding in the relation shown. The head element 79 is preferably of light meta-l, snchas aluminum, andthe tail weight Si! i -is preferably of relatively heavy metal, such as a Zinc alloy;

As explained above, electrical windings may be assemi bled to the respective legs 7s-71 72 prior to the assembly of thelegs to each other. Thus, winding 81 on the left end of leg 72 may be developed at a first longitndiral location and winding 33 may 'oe developed (in the opposite sense) at a second longitudinal location; both windings 31-83 may be developed from the same conductor, and joined by connector 82, with external connections available at lead ends ?yll-83'. Both winding developments may be made on conventional helical coil-winding appe- `ratus in a single chucked position of leg 72 and prior to assembly of leg 72 to the rest of the transducer. In a similar manner, separate opposed-phase windings 84-85, with leads &t -85', may be developed as a subassembly on leg 71; and opposed-phase windings 256- 87,

with leads 36- 7', may be developed as a sub-assembly on leg Th. `In assembling the wound legs to each other` (at spacer blocks 73-74 .,73) and in 'electrically interconnecting the Winding leads, care must be taken that the adjacent windings 81-84 are oppositely Wound 01' :oppositely energized and that 'the adin-cent windings- 84-86 are oppositely wound or energized. The leadsmay be intercon'nected in series or in parallel in a manner determining the desired relative direction of fiux circulation, as indicated by the phantom arrows in Fig. 8.

I 'It will be seen that I have described an improved transducerconstruction particularly applicable to low-frequency use wherein it 'is important to maintain utm'ost eiiiciency and `assurance against fiux lealrage between closeiy adjacent legs of any given flux path. My .basic 'Construction is inherently applicable to any length, and the ernployment of plural longitudinally adjacent independent fiux paths assures against fluxlosses. in spite of the apparent complexity of structure, it is nevertheless applicable to relatively inexpensive assembly because, as indicated particularly in connection With Figs.'7 and '8, con- Ventional coil-Winding techniques are applicable prior to assembly of wound sub-assemblies. Long transducer'elements may be housed inside metal tubes with end closures tomake oscillators for drilling, shake tables,-lapping a devices, and the like; in the latter connection, Figs. S and 6 may be viewed as essentially longitudinal sectional views through the tubular housing in which parts labelled 59-68 are essentially the same tu'bular housing part. The high amplitudes developed at low frequencies are advantagei ous in very long transducerslofthe 'type shown'in Figs.

iinmersed applications, and if corrosion-resistant materials are employed, including, tor example, windings developed With polytetrafluoroethylene-insulated ccndnctors, my invention permits tne use of unhoused constructions', or, alternatively, constructions in which the housings are fiooded, as will be understood.

While I have described the invention in detail for the preferred forms shown, it will be understood that'rnodifications may be made within the scope of the invention as' described in the clairns which follow.

I claim: 1. An electromechanical transducer, comprsing two separate laterally spaced elongated-legs ofmagnetostrictive material, separate blocks of magnetic -flux-conducting material* magnetically connecting corresponding end portions of said legs, a further block -of magnetifluxconducting material magnetically connecting corresponding 'intermediate portions of said legs, saidinte'rnediate block being a permanent magnetand therefore establish- ,ing-polarized `flux-conducting paths on the one 'hand through said 'legs and said-intermediate block and the block at one end, and on the other hand through said e 1egs and said intermediate block and the block ;at the other-end, and winding'meanszlinked separately to said 'paths along-said legs -and in a polarity tocirculate :flux in opposite-directions in-saidpaths. 2. An' electromechanical transducer, -com prsing ?two separate laterally spaced elongated legs, each :leg comprising a consolidated -stack of like longitudinally extendingmagnetostrictive strips, separate blocks' of-magnetic finx-conducting material rnagnetically .connecting corresponding endportions of said legs, awfurther block of r magnetic fiux-conducting material "magnetically connecting corresponding intermediateportions otsad legs,:sai-d connecting corresponding end portions of said legs, a

v ing portions of saidlegs at a location longitudinally spaced second pair of magnetic flux-conducting blocks magnetcally connecting corresponding intermediate portions of said legs, a third pair of magnetic flux-conducting blocks magnetically connecting the other corresponding ends of said legs, whereby separate fluxpathsmay be established between adjacent blocks 'and adjacent legs, means oppositely polarizing adja-cent flux -paths, and winding means linked to said flux paths along said legs and in a sense to develop circulating flux of opposite polarity in'adjacent flux paths, whereby `the instantaneousfiux in those portions ofthe intermediate log-which are common'to two adjacent flux paths may always flow .in the same'direction, and 'whereby the instantaneons fluxpassing through any single one of said intermediate'blocks may always be in the same direction-for eachof the two adjacentflux paths served thereby. v g

4. A transducer according to claim 3, in'which the outer legs are'of equalwidth and are each substantially one-half the wdth'of the intermediate leg. I

5 An electrornechanical transducer c vmp'rising three I laterally spaced elongated legs, each leg comprising a sepr arate consolidated stack of like longitudinally extending magnetostrictive strips, a first pair of 'separate blocks of magnetic fluX-conducting material magnetically connecting first corresponding end' portions of said legs, a second pair of separate blocks of magnetic fluX-conducting material magnetically connecting further correspondfrom said first corresponding portions, the blocks of one of said pairs being permanently magnetizedt and oriented to establish opposed polarity in the respective fluX-conducting paths defined on the one hand by a first two adjacent legs and by the magnetic blocks spacing the same and on the other hand by the other two adjacent legs and the magnetic blocks spacing the same, and separate windings coupled to the legs of said separate paths in a sense to circulate flux in opposite directions in adja cent of said separate paths. r

6. A transducer according to claim 5 and including i U head and tail weights bonded to the respective longitudinal ends of said legs.

7. In an electrical transducer, a core including a consolidated stack of like laminations of magnetostrictive material, each lamination including a plurality of laterally spaced elongated legs integrally forrned with a head joining said legs at one end and defining an elongated slot between two adjacent legs, a first single ferrite insert in said slot and longitudnally spaced from said head and defining with said head and With said adjacent legs a first fluX-conducting path, a second single ferrite insert in said slot and longitudinally spaced from said first insert on the opposite side thereof from said head and defining With said first insert and with said adjacent legs a second uX-conducting path, said first ferrite insert being permanently magnetized, whereby said flux-conducting paths are polarized in opposite directions, and Winding means linked to said separate paths in a sense to circulate flux in opposte directions in said paths.

8. In an electromechanical transducer, a core including a consolidated stack of like laminations of magnetostrictive material, each lamination including a plurality of laterally spaced elongated legs integrally formed with a head joining said legs at one end and defining an elongated slot between two adjacent legs, a first single ferrite insert in said slot and longitudinally spaced from said head and defining with said head and with said adjacent legs a first fiux-conducting path, a second single ferrite insert in said slot and spaced from said first insert on the opposite side thereof from said head and defining With said first insert and With said adjacent legs a second fiuX-conducting path, means magnetcally polarizing said ux-eonducting paths in opposite directions, and winding means linked to said paths in a sense circulating fiux in opposite directions in said paths.

9. In `an electromechanical trans ducer, a magnetostrictive core having a plurality of laterally spaced elongated legs extending in the same general direction, first uX-conducting means joining said legs at a first longitudinal location, second and third flux-condncting means joining said legs at second and third locations longtudinally spaced from each other and from said first location, the intermediate of said uxconductirg means being permanently magnetized, and Winding means coupled to one of said legs.

10. A tranducer according to claim 9, and including independent counterweights ndependently bonded to the respective ends of said core.

11. A transducer according to claim 10, and including mounting structure Secured to both said counterweights independently of said core.

12. A transducer according to claim 10, and including acoustic pressure-release means bondedrto the outer longitudinal exposed face of one counterweight to the exclusion of the other.

13. in an electromechanical transducer, an elongated t; magnetostrictive core having a plurality of laterally spaced elongated legs, first ux-conducting means joining said legs at a first longitudinal location, Whereby an elongated slot is defined between said legs, second flux-conducting means joining said legs at a second longitudinal location spaced from said first flux-condncting means and defining with said first flux-conductng means and With said legs a first fluxconducting path, third finx-conductng means joining said legs at a third longitudinal location and defining with said legs and with said second flux-conducting means a second tlux-conducting path, fourth flux-conducting means joining said legs at a fourth location and defining With said fiux-conducting means a third fluX-conducting path, means oppositely polarizng adjacent of said paths, nd separate Winding means linked to said respective in a direction to circulate fiux in opposite directions in adjacent paths.

14. in an electrcmechanical transducer, an elongated magnetostrictive core having plurality of laterally spaced elongated lcgs, first fiux-conducting means joining said legs at a first longitudinal location, whcreby an elongated slot is defined between said legs, second fluX-conducting means joining said legs at a second longitudinzl location spaced from said first flux-conducting means and defining With said first iluX-conducting means and with said legs a first lux-conducting path, third flux-conducting means j oining said legs at a third longitudinal location and defining With said legs and with said second flux-conducting means a second fiux-conducting path, fourth flxconducting means joining said legs at a fourth location and defining With said ux-conducting means a third fluxconducting path, said second flux-conducting means comprising a permanent-magnet insert, whereby said first and second paths are oppositely polarized, said third' fluxconducting means comprising a further permanent magnet insert Whereby said second and third paths' are oppositely polarized, said two inserts being oriented to polarize said second ux-cenducting path in the same direction, first Winding means including turns separately linked to a first two of said paths in a direction to circulate fluX in opposite directions in the same, and second winding means independent of said first windng means and linked to the remaining of said three paths.

References Cited in the file of this patent UNITED STATES PATENTS l,997,193 Kato et al. Apr. 9, 1935 2,4ll,9ll Turner Dec. 3, 1946 2,704,333 Calosi Mar. 15, 1955 2,745,084 Bundy May 8, 1956 FOREIGN PATENTS l,()66,3l9 France Jan. 20, 1954 856,079 Germany Nov. 20, 1952 

